Leakage current detection interrupter with open neutral detection

Abstract

A leakage current detection interrupter (LCDI) having open neutral detection. In one embodiment, the LCDI is formed in a plug and includes a circuit interrupter means for breaking a conductive path between line side phase and neutral conductors and load side phase and neutral conductors. A tripping means is coupled to operate the circuit interrupter means to break the conductive path upon the detection of the opening of the line side neutral conductor referred to as open neutral condition. The tripping means, which uses the neutral path as a return path if leakage current is detected, will, with this invention, use a line side ground conductor as a return path if the neutral path is broken anywhere between a service panel entrance and the plug. In response to the opening of the line side neutral conductor or leakage current, the LCDI interrupts the flow of current to a load such as a window air conditioner.

1 . A leakage current detection interrupter (LCDI) comprising: 
 a circuit interrupter means for breaking a conductive path between line side phase and neutral conductors and load side phase and neutral conductors; and    a tripping means coupled to the circuit interrupter means to break the conductive path in response to detecting an opening of the line side neutral conductor using a line side ground conductor as a return path.    
   
   
       2 . The leakage current detection interrupter of  claim 1  where the tripping means includes one or more diodes serially connected between an output of the tripping means and the ground conductor.  
   
   
       3 . The leakage current detection interrupter of  claim 1  where the tripping means includes a voltage divider circuit connected across the load side phase and neutral conductors with a voltage threshold to detect the opening of the line side neutral conductor.  
   
   
       4 . The leakage current detection interrupter of  claim 1  where the leakage detection interrupter is formed in an electrical wiring plug as part of an extension cord.  
   
   
       5 . The leakage current detection interrupter of  claim 1  where the tripping means includes a semiconductor controlled switch connected across the load side phase and neutral conductors where the switch conducts upon the opening of line side neutral conductor.  
   
   
       6 . The leakage current detection interrupter of  claim 1  where the circuit interrupter means includes a first normally closed switch connected between the line and load side phase conductors, and a second normally closed switch connected between the line and load side neutral conductors, where the tripping means causes the first and second switches to switch to an open position the opening of the line side neutral conductor, thereby disconnecting the line side conductors from the load side conductors.  
   
   
       7 . The leakage current detection interrupter of  claim 6  where the circuit interrupter means includes a solenoid coil to cause the first and second switches to switch an open position upon the opening of the line side neutral conductor.  
   
   
       8 . The leakage current detection interrupter of  claim 1  further comprising a shield conductor for connection between the tripping means and a load where the shield conductor conducts leakage current between the line and neutral conductors and the shield conductor.  
   
   
       9 . An electrical extension cord comprising: 
 an electrical cable including separate, insulated phase, neutral and ground conductors;    an electrical plug connected to a line side of the phase and neutral conductors and to a ground conductor;    a circuit interrupter means electrically connected to the line side phase and neutral conductors, and load side phase and neutral conductors; and    a tripping means coupled to operate the circuit interrupter means to electrically disconnect the line side phase conductor from the load side phase conductor upon detecting the opening of line side neutral conductor where the tripping means uses the ground conductor as a return path.    
   
   
       10 . The cord of  claim 9  where the tripping means includes one or more diodes serially connected between an output of the tripping means and the ground conductor.  
   
   
       11 . The cord of  claim 9  where the tripping means includes a voltage divider circuit connected across the load side phase and neutral conductors with a voltage threshold to detect the opening of the line side neutral conductor.  
   
   
       12 . The cord of  claim 9  where the leakage detection interrupter is formed in an electrical wiring plug as part of an extension cord.  
   
   
       13 . The cord of  claim 9  where the tripping means includes a semiconductor controlled switch connected across the load side phase and neutral conductors where the switch conducts upon the opening of line side neutral conductor.  
   
   
       14 . The cord of  claim 9  where the circuit interrupter means includes a first normally closed switch connected between the line and load side phase conductors, and a second normally closed switch connected between the line and load side neutral conductors, where the tripping means causes the first and second switches switch to an open position upon the opening of the line side neutral conductor, thereby disconnecting the line side conductors from the load side conductors.  
   
   
       15 . The cord of  claim 14  where the circuit interrupter means includes a solenoid coil to cause the first and second switches to switch to an open position upon the opening of the line side neutral conductor.  
   
   
       16 . The cord of  claim 9  further comprising a shield conductor for connection between the tripping means and a load where the shield conductor conducts leakage current between the line and neutral conductors and the shield conductor.